1. Field of the Invention
The present invention relates to a means of simultaneously compensating for propagation path distortion and frequency offsets suffered by a moving station or the like in digital wireless communication, and to a method of compensating for fading or frequency offsets in a propagation environment wherein one or the other occurs in digital wireless communication, and particularly to transmission method with compensation for fading distortion and frequency offset compensation and used as a propagation path distortion-compensation technique using pilot signals in mobile wireless communication.
2. Description of the Prior Art
In digital wireless communication using moving stations, fading caused by various changes in the environment and frequency offsets arising due to the movement of the station are known to occur. FIG. 1 shows the frame structure in a first related art used to compensate for the fading and frequency offsets that occur when the station moves. The unique word shown in FIG. 1 is a known symbol sequence and the pilot symbol is a known symbol. The receiver estimates the frequency offset of this unique word portion and estimates the fading distortion from the pilot symbol, and compensates for each, respectively.
However, with this method, each type of compensation is performed with a different type of known symbol, thus complicating the structure of the transceivers and reducing the fraction occupied by the data portion so there is a problem in that the transmission rate is reduced,
In addition, FIG. 2 shows an example of a second related art wherein two pilot symbols are disposed sequentially, and P1 or P2 or both are used to estimate fading and the frequency offset is estimated from the phase difference among the adjacent P1 and P2. This is a method of compensating for propagation path distortion by inserting two or more adjacent pilot symbols. However, with this method, phase differences between the adjacent P1 and P2 arising from the phase noise suffered by P1 and P2 occur, so the frequency offset may differ greatly from the estimated value of the frequency offset. In addition, if the phase difference reaches the vicinity of 180 degrees, the sign of the frequency may be reversed in the estimate.
Moreover, if three or more adjacent pilot symbols are used in order to reduce these phase errors, there is a problem in that the fraction occupied by the data portion is relatively reduced and the transmission rate is lowered.
As described above, with the first related art that uses unique words, there are problems in that the structure of the transceiver becomes complex and the fraction occupied by the data portion is reduced so that the transmission rate is lowered, and with the second related art that uses two consecutive pilot symbols, there are problems in that the frequency offset may be much different from the estimated value and if three or more adjacent pilot symbols are used, the fraction occupied by the data portion is relatively reduced, also lowering the transmission rate.